Google PageSpeed Insights now uses Lighthouse as its analysis engine.
This change was made in order to create consistency between Google’s web page performance analysis tools.
Previously, Google’s tools used different analysis engines which resulted in different recommendations from each tool.
Users can now get the same performance audits and recommendations on the web, from the command line, and in Chrome DevTools.

“At Google, we know that speed matters and we provide a variety of tools to help everyone understand the performance of a page or site. Historically, these tools have used different analysis engines. Unfortunately, this caused some confusion because the recommendations from each tool were different. Today, we’re happy to announce that Pagespeed Insights (PSI) now uses Lighthouse as its analysis engine.”

Going forward, PageSpeed Insights (PSI) will provide users with the following performance data:
Lab Data: PSI fetches and analyzes the page using Lighthouse, which simulates how a mobile device loads a page. It computes a set of performance metrics and summarizes data into a score from 0-100 (90 and up is considered good).
Field Data: Real-world performance metrics for the page and its origin, including First Contentful Paint and First Input Delay.
Opportunities: Suggestions on how to improve the page’s performance metrics, as well as estimations of how much faster the page will load if the improvement is implemented.
Diagnostics: Additional information about how a page adheres to best practices for web development.

PageSpeed Insights API Updates
Google will also be rolling out an updated version of the PageSpeed Insights API.
Version 5 of the PSI API will provide Chrome User Experience Report Data, in addition to all of the Lighthouse audits.
Previous versions of the PSI API will be deprecated in six months.

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